Devices for the automated release of liquid medicaments are normally used with patients who have a continuous and, in the course of the day, may have a varying need of a medicine that can be administered by subcutaneous infusion. Specific applications are, for example, certain pain therapies and the treatment of diabetes, in which computer controlled infusion pump devices are used, such as insulin pumps. Such devices can be carried by a patient on the body and contain a certain amount of liquid medicament in a medicine reservoir in the form of a container. The medicine reservoir often contains enough medicine for one or several days. The liquid medicament is supplied to the patient's body from the medicine reservoir by subcutaneous infusion of injection, through an infusion cannula or an injection needle.
As used herein, the terms “medicament” and “liquid medicament” are meant to encompass any drug-containing liquid medicine, or therapeutic or diagnostic liquid, capable of being passed through a delivery element such as a hollow needle in a controlled manner, such as a liquid, solution, gel or fine suspension. Representative drugs include pharmaceuticals such as peptides, proteins, and hormones, biologically derived or active agents, hormonal and gene based agents, nutritional formulas and other substances in both solid (dispensed) or liquid form. In particular, the term medicament encompasses insulin preparations ready for administration.
The terms “subcutaneous infusion” and “subcutaneous injection” are meant to encompass any method in which a needle device is inserted at a selected site within the body of a patient for subcutaneous, intravenous, intramuscular or intradermal delivery of a liquid medicament to a subject. Further, the term needle defines a piercing member (including an array of micro needles) adapted to be introduced into or through the skin of a subject.
Particularly in self-administration of liquid medicaments, patients using the medicament and administering it desire convenience and discretion. As a consequence, the dimensions of such infusion devices are limited. However, the overall length, width and thickness should be as small as possible to remain hidden under clothing and to be comfortably carried.
While there are fully or partly disposable single-use infusion pump devices, such devices are typically non-disposable and are loaded with a disposable drug cartridge. Disposable cartridges are preferable for sterility and contamination prevention reasons. They may be delivered pre-filled with a certain liquid medicament, or empty, ready to be filled by a user. The self-filling of containers has the advantage that medicaments that are not readily available in pre-filled containers can be used for such infusion pump devices, thereby providing the patient with a larger choice of sources for his medicaments. Furthermore, the stability of many medicaments in liquid form, particularly in plastic containers, can only be guaranteed by the manufacturer for a certain amount of time.
The standard infusion pump devices that are carried on or near the body have a medicine reservoir with a cylindrical ampoule and a displacement piston, which is pushed into the ampoule by a piston rod or threaded spindle in order to convey the liquid medicament. These known designs have the disadvantage of being longer and/or thicker than desired, therefore, the resulting dimensions are not adequate for compact infusion pumps.
To reduce the overall volume of an infusion pump device, the syringe-type dosing mechanism can be replaced by a downstream pump system. In such a device, a miniaturized pump is arranged downstream of the main reservoir and causes a suction pressure that conveys the product from the reservoir to its destination. The reservoir in this type of an infusion pump device is realized as a flexible container. Such a flexible container may, for example, have the form of two flexible wall sheets that are sealed together. Flexible containers have the advantage of a smaller volume surplus of the container in relation to its content, which reduces the manufacture costs and the achievable dimensions of an infusion pump device using such a flexible container. The volume of a flexible container for use in an infusion pump device may be up to 10 ml, for example. A typical range for diabetes therapy is 1.5 to 3.5 ml. For other therapies, e.g. pain therapy, that use other administration regimes, other volume ranges may be more preferable.
A common problem of flexible containers, as they are known, is air remaining in the container. If, for example, a flexible container is empty and is filled with the appropriate liquid medicament by the user himself, there may be a certain amount of air in the container after the filling process. If the air remains in the container or in the fluidic system of a pump system, air bubbles may be administered instead of the liquid medicament, which leads to potentially dangerous dosing errors. Furthermore, the administration of air into a patient's body should generally be avoided for medical reasons. Another negative effect of air present in the fluidic system of an infusion pump device is the reduced stiffness of the fluidic system. Due to the high compressibility of gases, such as air in relation to liquids, it becomes difficult to detect blockages or occlusions in the fluidic system of an infusion pump device by measuring the fluidic pressure, because the air reduces the pressure increase that occurs in case of an occlusion.
Filling a container with a liquid medicament with prior removal of air from the container and without air bubbles getting into the container requires skill The user is generally an untrained person, such as the patient himself or a relative. Reservoir containers can be filled by transferring the liquid medicament with a syringe. Syringes are typically inexpensive, but certain manual skills are needed for their proper use. Many patients with motor difficulties, such as diabetics with neuropathy or the elderly, have problems with safely handling syringes. In addition, accidental needle injuries and transferring the proper amount of medication pose concerns. Another problem is cross-contamination of medications between containers.
Present devices should help a user fill a container for infusion pump systems. Those devices, however, are intended for the use in syringe/ampoule type infusion pump systems and cannot be properly used with flexible containers.
Present devices have an infusion system with a flexible reservoir container arranged in a rigid casing and fluidly connected to a liquid in a supply container under ambient pressure. When a vacuum pump reduces the pressure inside of the rigid casing, the resulting pressure differential between the rigid casing and the supply container conveys the liquid into the flexible container. To avoid air, instead of liquid, being emptied into the flexible container from the supply container, the user has to correctly orient the supply container. Because a user usually does not have medical training, such a system is prone to incorrect operation and handling errors. Furthermore, present devices do not allow evacuation of the flexible container prior to filling.